New method analyzes ink additives

On January 14, 2014 the peer-reviewed journal Food Additives & Contaminants: Part A published the article “Multi-analyte methods for the detection of photoinitiators and amine synergists in food contact materials and foodstuffs – Part II: UHPLC-MS/MS analysis of materials and dry foods” reporting on a new, efficient and sensitive high throughput method for the batch analysis of photoinitiators and amine synergists in food contact materials (FCM) and food stuff. The aim of the study by Teelke Jung from the regulatory enforcement agency CVUA in Stuttgart and Thomas Simat from the Technical University in Dresden, both in Germany, was the development of a multi-substance method for the concurrent analysis of 53 additives of printing inks and varnishes. The researchers setup an ultrahigh performance liquid chromatography diode array detection double mass spectrometer (UHPLC-DAD-MS/MS) method able to detect 49 of the targeted additives at a maximum level of detection (LOD) of 10 µg kg-1. This level is at the moment only regulated in Switzerland for toxicologically unevaluated additives (EDI 2005), but also considered to be relevant in the EU.

Photoinitiators and amine synergists are ingredients of inks and coatings which decompose into free radicals by induction of ultra-violet, visible and near infra-red radiation and subsequently trigger polymerization processes leading to the curing of dyes and coated surfaces. This type of curing is thought to be more environmentally friendly than the previous application of organic solvents. However, these chemicals and their reaction products can migrate into foodstuff and potentially endanger human health. Chemically, photoinitiators and amine synergists belong to the classes of benzophenones and ethylbenzophenone isomers, among others. The chemicals were measured at parts per million (ppm) ranges in dyes and FCMs. In particular 4-methylbenzophenone raised concerns in 2009 when it was measured in cereal products by German and Dutch authorities at elevated concentrations of 798 μg/kg and 3729 μg/kg, respectively (EFSA 2009). Subsequently the European Food Safety Authority (EFSA) concluded that measured concentrations might imply a health risk if consumed continuously at these levels.

In the present study, extraction was performed for 8 FCM samples: 3 plastic cups for dairy products, 1 disposable plastic drinking cup, 1 paper label used on plastic bags for pastries and 3 carton board packs for dry food. Sample extraction was performed using acetonitrile at 70°C for 24 h in a shaking water bath.

Jung and Simat also used their method for the analysis of dry foodstuffs. 8 kinds of breakfast cereals (including muesli with chocolate bites, yoghurt drops, dried fruits etc.) were prepared in 10 g portions of surrogate for dried foodstuff, to which reference doses of photoinitiators and amine synergists were added at 4 concentration levels (10, 50, 250 and 1250 μg kg−1). Results for the dried foodstuffs show that the extraction recovery rate for more than 87 % of substances lay between 70 % and 120 % and was therefore satisfactory. Further, the variance among results was rather low with only one exception, with a standard deviation of more than 12 %.

Concluding, Jung and Simat state that 52 chemicals can be analyzed in a single run taking as little as 11.5 min to be achieved, thus enabling a high throughput. 49 chemicals can be detected by MS/MS and further 3 by means of diode array detection (DAD). The extraction procedures are characterized by the study’s authors as simple and easy-to-perform, additionally supporting the testing of large batches of samples in a short time by the UHPLC-DAD-MS/MS method. The authors are confident that the method can be used for migration testing with standard food simulants like ethanol and Tenax® (poly(2,6-diphenyl-p-phenylene oxide)), though this was not part of the present study. On the other hand, quantification was not achievable for all chemicals. For example, some photoinitiators with the chemical structure of the methylisomers of benzophenone were not distinguishable in MS/MS spectra and they could therefore not be quantified. Here, more sophisticated procedures are needed. Nonetheless, the authors argue that the presented method allows for a comprehensive analysis of potential photoinitiators and amine synergists migrants found in FCM as well as in food stuff. Above all, the new method is interesting for official control laboratories that are screening unknown compositions of ink applied to food packaging where a targeted procedure for specific compounds of interest is not applicable.

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